Shielding and Radiation Measurements at ESRF

Transcription

1 Shielding and Radiation Measurements at ESRF Radiation Safety Meeting SOLEIL Synchrotron, 18 October 26 P. Berkvens European Synchrotron Radiation Facility Radiation protection policy at the ESRF Storage ring shielding Beamline shielding: bremsstrahlung 1/37

2 ESRF Accelerator characteristics: E = 6 GeV I = 2 ma L = 843 m Lifetime: Multibunch (2 ma): 75 h 16-bunch (9 ma): 9 h 2/37

3 Radiation Protection Policy at the ESRF A large number of people come to the ESRF to stay for a relatively short period of time: Users Contractors Visitors 8 % of experiments macromolecular crystallography 6 X-ray imaging material science 4 2 typical duration of experiments at the ESRF number of 8-hours shifts 3/37

4 Radiation Protection Policy at the ESRF No radiation workers < 1 msv.y -1 (.5 μsv.h -1 ) Dose rate varies strongly, e.g. during injection and beam trips limit on dose rate not possible débit de dose(μsv.h -1 ) photon dose rate (μsv.h -1 ) stored faisceau stocké(ma) beam (ma) temps (jours depuis days le 28/3/3) 4/37

5 Radiation Protection Policy at the ESRF No radiation workers < 1 msv.y -1 (.5 μsv.h -1 ) Dose integrated essentially during machine studies and start-up débit de dose (μsv.h -1 ) photons photons faisceau stocké (ma) integrated dose (μsv) stored beam (ma) neutrons neutrons limit on annual dose not sufficient temps (jours depuis le 18/1/2) days 5/37

6 Radiation Protection Policy at the ESRF H 4hours ( ) 1 d dt 4.5μSv. h = 2 μsv No radiation workers < 1 msv.y -1 (.5 μsv.h -1 ) Interlocked radiation monitors: Storage ring: 64 neutron monitors Interlock on injection Beamlines: 1 ionisation chamber per beamline Interlock on front end 6/37

7 Storage ring shielding 1 cm hall expérimental experimental hall 1 cm 1 cm 1 cm 12 cm 12 cm galerie technique technical gallery 12 cm variable: variable: de 12 cm à 3 cm from 12 to 3 cm 2 cm béton lourd hématite, densité = 3,8 g.cm -3 heavy (haematite) concrete density = 3.8 g.cm -3 7/37

8 Storage ring shielding 8 7 nsv / kj intercepté nsv (photon) / kj intercepted shielding measurements analytical model: 1 21,3 5 e = 2, higher μsv 1 beam faisceau distance le long de l axe du faisceau [m] distance along beam axis (m) CV-5 ID vessel beam intercepted on vacuum valve CV-5 chambre faisceau intercepté par vanne de vide 8/37

9 Storage ring shielding shielding measurements 35 débit de dose [µsv/h] ambient dose equivalent (μs/h) analytical model: 3 25 photons: x 2 5 e 1 21,3 2,1 2,3 = 3 msv / h 2 15 neutrons: x 1 23 e 1 17,39 2,1 2,3 Neutrons 1 5 2,7 e + Photons 2,1 2,3 = 3 msv / h 1 Neutrons 5 Photons distance along beam-axis (m) distance le long de l axe du faisceau [m].3 kw faisceau beam 9/37

10 Storage ring shielding shielding measurements electron losses (% of total loss /m) puissance e - perdue [% puissance faisceau / m] calculated calculé débit de dose en neutrons [Sv/h par kw faisceau incident] neutron ambient dose equivalent (Sv/h per kw total loss) calculé mesuré calculated perte localisée measured calculated (point loss) distance along beam axis (m) distance le long de l axe du faisceau [m] beam faisceau e - beam intercepted on vacuum valve 1/37

11 Storage ring shielding shielding measurements summary shielding measurements: photons:.8 μsv.kj -1 neutrons: 1.6 μsv.kj -1 injected electron charge average beam loss power: 12 μc injected per year 275 μc per 2 h at 6 GeV, 165 kj par 2 h (mc) μc per day 5 full current injections per day days since 1/1/99 completely determined by start-up and R&D 11/37

12 Storage ring shielding des pertes totales 1 shielding measurements summary shielding measurements: photons:.8 μsv.kj -1 neutrons: 1.6 μsv.kj -1 % of total beam losses 1 Injection: 165 kj per 2 h 1 1 % of losses : kj par 2 h ( ) 16.5 = 4 μsv per 2 h (.2 μsv/h) c1 c2 c3 c4 c5 c6 c7 c8 c9 c1 c11 c12 c13 c14 c15 c16 c17 c18 c19 c2 c21 c22 c23 c24 c25 c26 c27 c28 c29 c3 c31 c32 1 % of losses : 165 kj par 2 h ( ) 165 = 4 μsv per 2 h (.2 μsv/h) numéro de la cellule cell number 12/37

13 Storage ring shielding 1 local beam losses: injection area cell ma 2 cell days 13/37

14 Storage ring shielding 1 local beam losses: in-vacuum undulators cell cell ma days 14/37

15 Storage ring shielding 1 local beam losses: 8 mm ID vessel cell cell ma days 15/37

16 Storage ring shielding H 4hours 1 ( d ) dt 4.5μSv. h = 2 μsv 64 neutron monitors correction for photon dose 1 cm hall expérimental experimental hall 1 cm 1 cm 1 cm 12 cm 12 cm galerie technique technical gallery 12 cm heavy (haematite) concrete density = 3.8 g.cm -3 variable: variable: de 12 cm à 3 cm from 12 to 3 cm 2 cm béton lourd hématite, densité = 3,8 g.cm -3 16/37

17 17/37

18 18/37

19 photons: net integrated dose (μsv)( neutrons: net integrated dose (μsv) days /37

20 14 total dose (μsv) cell 13-1 cell μsv/h days days 2/37

21 12 1 cell 27-1 cell μsv/h total dose (μsv) days days 21/37

22 25 2 cell 29-1 cell μsv/h total dose (μsv) days days 22/37

23 25 2 cell 29-1 cell μsv/h total dose (μsv) days days 23/37

24 Gas-bremsstrahlung gas-bremsstrahlung power: de P = C e dx 2 2 P Ee I ( E ) p I L, L electron stopping power pressure in straight section electron beam intensity length of straight section de dx ( E ) ESRF SRS Diamond Soleil Energy (GeV) Current (ma) Straight section (m) Bremsstrahlung power (normalised to ESRF) e p E E e e I 24/37

25 Gas-bremsstrahlung Example: typical ESRF Optics Hutch 6 GeV 2 ma mbar photon effective dose rate (μsv.h -1 ) distance along hutch (cm) mm 3 mm 6 mm 9 mm 12 mm 15 mm 18 mm 21 mm 24 mm 27 mm 3 mm primary slits (Cu) 1 cm Pb screen, 2 cm, 2 x 2 cm 2 monochromator + W beamstop 1 cm, φ 6 cm écran en Pb, épaisseur 2 cm, 2 x 2 cm 2 fentes primaires en Cu mirror miroir en Si(Si) monochromateur avec arrêtoir en W, épaisseur 1 cm, φ 6 cm 12 cm 5 cm 1 cm 15 cm 2 cm 25/37

26 Gas-bremsstrahlung 1.E+ 1 effective dose rate (μsv.h -1 ) Example: typical ESRF Optics Hutch Sidewall: 3 cm Pb 6 GeV 2 ma mbar photons neutrons 1.E E distance along hutch (cm) primary slits (Cu) 1 cm Pb screen, 2 cm, 2 x 2 cm 2 monochromator + W beamstop 1 cm, φ 6 cm écran en Pb, épaisseur 2 cm, 2 x 2 cm 2 fentes primaires en Cu mirror miroir en Si(Si) monochromateur avec arrêtoir en W, épaisseur 1 cm, φ 6 cm 12 cm 5 cm 1 cm 15 cm 2 cm 26/37

27 Gas-bremsstrahlung radiation levels outside beamlines 5 dose (μsv) photon sidewall photon backwall neutron sidewall neutron backwall current (ma) days since 23/1/1 27/37

28 Gas-bremsstrahlung id6 on-axis bremsstrahlung measurements 28/37

29 Gas-bremsstrahlung Gy/h/mA 2 1.E-4 On-axis bremsstrahlung measurements during initial conditioning of ESRF 5 m long, 8 mm internal height NEG-coated extruded aluminium ID vessels 1.E-5 2 orders of magnitude 1.E-6 factor days continuous operation at 185 ma 1.E electron dose (A.h) 29/37

30 Gas-bremsstrahlung 1.E-3 Gy/h/mA 2 1.E-4 run 26-1 run 25-5 Series3 1.E-5 1.E electron dose (A.h) 3/37

31 Gas-bremsstrahlung photon dose (μsv/h) example: id21 radiation measurements outside optics hutch penning 4 (mbar) 1.6E-8 1.4E-8 1.2E-8 1.E uniform 2 x 1/3 8.E-9 6.E-9 4.E-9 2.E bunch shutdown days.e+ 31/37

32 Gas-bremsstrahlung.7 photon dose (μsv/h) example: id19 radiation measurements outside optics hutch.6.5 vacuum intervention ma days 32/37

33 Gas-bremsstrahlung Bending magnet beamlines faisceau electron d électrons beam line source of bremsstrahlung length of trajectory = 24.4 cm source de rayonnement de freinage: longueur de la trajectoire = 24,4 cm absorbeur en cuivre crotch absorber 1 mrad 1 mrad 1 mrad o /64 = 5, o o length of trajectory = 2.4 m longueur de la trajectoire = 2,4 m 33/37

34 Gas-bremsstrahlung μsv.h bm8 doserate bm8 dose μsv per 4 hours ma time (days) 34/37

35 Other sources of bremsstrahlung Other sources of bremsstrahlung have to be considered, in particular bremsstrahlung produced by the scraping of electron beam. This occurs in the case of: Small gap ID vessels In-vacuum undulators At the ESRF, the effect is far less important than the effect of gasbremsstrahlung. The settings of the vertical scrapers is important. 35/37

36 Radiation monitoring outside optics hutches measured dose rate increased dose rate during injection. D net. D back. D meas time beam decay front end closed or no beam in SR D tot < 2μSv, t 4 t D dt hours t neutrons 2 photons back meas < D 3 μsv 36/37

37 Radiation monitoring outside optics hutches 37/37